Really? Have you gone back and watched it recently? IMO its unwatchable. That's generally the nature of comedy, it rarely ages well, and SNL is no exception
This is an excellent and underrated point that deserves further exploration. It's worth saying: Comedy ages faster than other types of content. I watched a ton of animation as a kid and most of it (Darkwing Duck, Rugrats, Tailspin, Bobby's World) fits well enough into most of today's animation lineups (DuckTales Reboot, Gravity Falls, Loud House). However, almost nothing from sketch comedy (SNL, Mad TV) or stand-up holds up well (or at all) unless it becomes preserved in our collective imagination as a cultural touchstone (Cowbell, Farley's "Down By the River," Carlin's seven dirty words, Chapelle's racier stuff).
I'll go so far as to say Comedy ages poorest of all entertainment mediums. I agree with you - barely anything from 80s SNL is entertaining, much less worthy as Cable TV filler. I would otherwise say Comedy serves better as a time capsule, but even then it fails because 80s SNL might as well be from the 60s. 2002 SNL might as well be from 1988, etc - that's how poorly comedy ages.
I think the lasting value of SNL is:
1) Their ability to invite on audience, on lighter terms than tuning into Maddow or Tucker, to be a part of the times. SNL's most memorable parodies of politicians (Carvey's Ross Perot, Fey's Sarah Palin, Baldwin's Trump) don't succeed because they are particularly funny - they succeed because of how well they play off the current headlines. SNL is more adept at living up to the moment, not so much creating a lasting moment.
2) Their very well managed growth of talent. A few years of proving yourself under watch of SNL is often the springboard for later earning a late night show, hosting an awards show, or landing comedy movie roles on your way to becoming a household name. SNL is able to compound this success by even recently inviting former cast members like Kristen Wiig, John Mulaney, and Adam Sandler to host shows. It works because it turns into a nostalgic experience for the audience, and nostalgia, as cheap and shallow as it is, works on an escape-seeking audience way more often than not.